[Bug ld/25384] New: Copy relocations and BIND_NOW on POWER ELFv1 results in crashes

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=25384

            Bug ID: 25384
           Summary: Copy relocations and BIND_NOW on POWER ELFv1 results
                    in crashes
           Product: binutils
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: ld
          Assignee: unassigned at sourceware dot org
          Reporter: fweimer at redhat dot com
  Target Milestone: ---
            Target: powerpc64

Created attachment 12203
  --> https://sourceware.org/bugzilla/attachment.cgi?id=12203&action=edit
libshared.so

This script produces a ./main executable which crashes when run:

cat >like-pthread.c <<EOF
void
implementation (void)
{
}
EOF
gcc -fPIC -shared -o liblike-pthread.so like-pthread.c -Wl,-z,now

cat >like-dl.c <<EOF
extern void implementation (void) __attribute__ ((weak));
void
use_implementation (void)
{
  if (implementation != 0)
    implementation ();
}
EOF
gcc -fPIC -shared -o liblike-dl.so like-dl.c -Wl,-z,now

cat >shared.c <<EOF
extern void use_implementation (void);
extern void _exit (int);

void
call_dlopen (void)
{
  use_implementation ();
  _exit (0);
}
EOF

cat >main.s <<EOF
        .section .rodata
ptr:
        .quad alias
        .weakref alias, implementation
        .section        ".opd","aw"
        .align 3
        .globl main
main:
        .quad   .L.main,.TOC.@tocbase
        .text
        .type   main, @function
.L.main:
        bl call_dlopen
        nop
EOF

gcc -fPIC -shared -o libshared.so shared.c -Wl,--no-as-needed -L. -llike-dl
-llike-pthread
gcc -Wl,-rpath,. -o main main.s -Wl,--no-as-needed -L. -lshared


It reproduces with binutils 2.27 and the current master branch in Git (at
commit 7a6bf3becbe3e0ce47d2681edcfe7adcb67fe4e2).

GDB says this:

Program received signal SIGSEGV, Segmentation fault.
0x0000000000000000 in ?? ()
(gdb) bt
#0  0x0000000000000000 in ?? ()
#1  0x00003fffb7d008c8 in use_implementation () from ./liblike-dl.so
#2  0x00003fffb7f50918 in call_dlopen () from ./libshared.so
#3  0x0000000010000784 in main ()

The construct in use_implementation was previously discussed here:

  <https://www.sourceware.org/ml/gnu-gabi/2016-q1/msg00004.html>

This crash arises when current glibc is built with --enable-bind-now (see the
downstream report; our 2.17 build includes the --enable-bind-now changes in
glibc master).

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